[ARC5] ARC R-511 Capacitor Failure

[Don Merz]

 What about some more modern current protection devices like PTC resettable fuses and the TVS? 
73, Don Merz, N3RHT

    On Tuesday, January 29, 2019, 8:41:29 AM EST, Michael Hanz <aaf-radio-1 at aafradio.org> wrote:  
 
  Fuses are notoriously inaccurate in their operation.  I use an old HP 0-40v 5A supply from a hamfest that I discovered had an unlabled overcurrent crowbar circuit added to it sometime after manufacture.  When you set it to a few milliamperes over the normal current draw of the radio, it shuts the voltage output down to zero whenever the current exceeds that set figure.  It's a bit touchy to set the crowbar control at first, but if you are going to do any testing for any length of time, it's a useful safeguard.  However, I can't emphasize enough the need to frequently check electrolytic capacitor temperatures when you're evaluating an old set, especially if for some reason you haven't been able to check electrolytic leakage currents.  A laser infrared thermometer is really useful for that function - it does reduce the burned finger syndrome. 
 
          73,
 - Mike  KC4TOS
 
 On 1/28/2019 4:22 PM, kn7sfz wrote:
  
 
So, if you have a radio that is otherwise running fine with the original caps, what might be a proper size fuse to put inline with the HV to protect the dynamotor and everything else downstream? (unobtrusive mod easily reversed)
 
 de Richard kn7sfz
 
 
 
 On 1/28/2019 1:12 PM, Kenneth G. Gordon wrote:
  
 On 28 Jan 2019 at 20:58, J Mcvey via ARC5 wrote:

 
 The filter cap on the HV line is the only one I've seen totally short. the others are 
usually just leaky as hell.
 
 I had one of those triple section 0.22 mfd job short out while I was using a receiver. As you 
say, bogged the dynamotor down like mad. Lucky I was right beside it when this happened.

 
 I had a similar event with an ARC-5 R-23 . It was running fine for about an hour 
when all of a sudden i heard the dynamotor bog down and the radio went dead. I 
was right next to it, so i hit the switch quickly. Fortunately ,there was no 
explosion. After that, my SOP is open and re-stuff all of the "flower pots".
Even the leaky ones degrade the performance and cause a higher current drain, 
so it's better to replace them and be done with it.
 
 I completely agree with you on this one. By now ALL of those things are leaking or shorted.

If one wants to have his receiver remain completely stock, then put it on a shelf and look at 
it. 

If one wants to have his receiver LOOK completely stock, yet wants to USE it, then restuff 
them. 

Otherwise replace every darned one of them with modern caps, before something 
irreplaceable burns up.

Ken W7EKB
 
 
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